Joe Pendleton (Warren Beatty), a backup quarterback for the American football team Los Angeles Rams, is looking forward to leading his team to the Super Bowl. He is riding a bicycle through the Mulholland Drive tunnel under Sepulveda Boulevard in Los Angeles when he collides with a truck. An over-anxious guardian angel (Buck Henry) on his first assignment plucks Joe out of his body early in the mistaken belief that his death is imminent, and Pendleton arrives in the afterlife.
Once there, he refuses to believe that his time was up, and upon investigation, the mysterious Mr. Jordan (James Mason) discovers that he is right; he was not destined to die until much later. Unfortunately, his body has already been cremated, so a new body must be found. After rejecting several possibilities (men who are about to die), Joe is finally persuaded to accept the body of millionaire industrialist Leo Farnsworth. Farnsworth has just been drugged and drowned in his bathtub by his wife Julia (Dyan Cannon) and her lover, Farnsworth's personal secretary, Tony Abbott (Charles Grodin).

Julia and Tony are naturally confused when Farnsworth reappears, alive and well. Leo Farnsworth buys the Los Angeles Rams in order to lead them to the Super Bowl as their quarterback. In order to succeed, he must first convince, and then secure the aid of, long-time friend and trainer Max Corkle (Jack Warden) to get his new body into shape. At the same time, he falls in love with an environmental activist, Betty Logan (Julie Christie), who disapproves of Farnsworth's policies and actions.
As the film's plotline heads toward the Super Bowl, the characters all face a crisis. Julia and Abbott continue their murderous plans, and Abbott shoots Farnsworth dead. The Rams are forced to start another quarterback, Thomas Jarrett, in the climactic football game. After a brutal hit on the field, Jarrett is himself killed. With Mr. Jordan's help, Joe then occupies his final body, that of Jarrett. Joe, in Jarrett's body, is shown leading the Rams to victory.

During the team's post-game victory celebration, Mr. Jordan removes Joe's memory of his past life and departs. Joe becomes Thomas Jarrett and the cosmic balance is restored; the winning quarterback, Jarrett, is shown meeting Betty after the celebrations have ended, and as the film ends it is strongly implied that they are falling in love as a result of a mutual sense of déjà vu.